Transformer



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G. CAMILLI TRANSFORMER June 11, 1929.

Filed Oct. 10, 1928 2 Sheets-Sheet bHm f 4 i lrno cam i I I i y H isAttO1 11 ey.

lvwvevwtora the ma netic losses in these parts maybe coni Patented June11, 19 29.

UNITED STATES 1,111,347 PATENT OFFICE.

GUGLIELMO CAMILLI, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TRANSFORMER.

Application filed October 10, 1928. Serial No. 311,639.

My invention relates to transformers and more particularly totransformers having concentric cylindrical windings. When a transformeris in operation, the main mag-- netic flux is substantially confined tothe core. The action of the primary and secondary Currents also producesa leakage fluxbetween the two windings. This leakage flux, after flowingbetween the windings, returns through the easiest path which it can findand the return path for a large part of the leakage flux often includesmagnetic material near the core and windings such as the core clampingstructure and the metal casing in which the transformer may be enclosed.The-flux in these adjacent magnetic parts results in magnetic losses anddecreased efficiencyof the transformer and it is the general object ofthe invention to provide an improved arrangement for controlling andreducing the external leakage flux and the ma netic losses caused by it.

he invention will be better understood from the following descriptiontaken in connection with the accompanying drawings in which Fig. 1 is aperspective view of a shell type transformer provided with means forreducing the external leakage flux; Fig. 2 is a similar view of a coretype transformer; Fig. 3 is a similar View of a three phase core typetransformer and Fig. 4 is a view of a transformer like that shown inFig. 1- but with a different arrangement of windings.

Like reference characters indicate similar parts in the differentfigures of the drawings.

The transformer shown in Fig. 1 is of the shell type with a magneticcore 10 having a central winding leg and two outer legs joined at theirends by yokes. The central winding leg is surrounded by the twowindings-11 and 12. The main magnetic flux is substantially confined tothe core. The currents in the two windings produce a leakage fluxthrough the space between them and returning through the easiest pathwhich it canv find. The return path for a considerable part of theleakage flux often includes magnetic material outside of the core andwindings. This magnetic material may include the core clampin structure,the metal casing which may enc ose the transformer and other adj acentmagnetic parts. Under these conditions,

siderab le so as to reduce appreciably the efficiency of thetransformer. These losses appear as heat, too, and provision fordissipat mg this heat in addition to that from the transformer itselfmust be madeor excessive temperatures may result.

As shown in'Fig. 1, the leakage flux is largely. prevented from leavingthe space between the two windings and reaching adj acent magneticmaterial by conductive members 13. con nected by conductors 14 to formclosed circuits close to the ends of the windings and a in front of bothends of the space between the windings. There are four of the conductivemembers 13, two at each end of the outer winding and extending along andclose to the ends of this winding on'opposite sides of the core. Theends of each member 13 are connected by conductors 14 tothe ends of themember 13 which is at the same end of the winding 1.2 and on theopposite side of the core, the conductors 14 extending around the outeredge of the core to avoid a short circui ted turn around the centralwinding leg of the core. It is apparent that no substantial amount ofleakage flux can leave the space between the two windings except throughthe core under the conductors 14. Any magnetic material near the coreand windings is thus efiectively shielded and protected. It

tained in most cases if the conductive members 13 extend along the outerface of the winding 12 and near its ends, the members 13 being as closeto the winding as is-practicable with the necessary insulation betweenthem. The conductive members 13 and the conductors 14 connecting themaround the outer edge of the core are shown in Fig. 2 as applied to acore type transformer. The core 10 has two winding legs, each surroundedby two windings" 11 and 12. This core has only a single opening and eachset of windings passes through the core only once so that only onemember 13 is necessary at each end of each of the outer windings 12, thetwo ends of two windings 11 and 12. The set of windings V,

on the central winding leg passes through the core twice so that twomembers 13 connected by conductors 14 are necessary at each'end of thisset of windings. The set of windings on each of the outer winding legspasses through the core only once sothat only one member 13 with itsends connected by a conductor 14 is necessary at each end of each ofthese sets of windings.

The transformer shown in Fig. 4 is similar to that shown in Fig. 1except that the winding 11 is formed in two concentric spaced sections.The-winding 12 is interposed concentrically between the two sections ofthe winding 11 and spaced from each of those sections. With thisarrangement, the leakage flux is induced in the two spaces inside andoutside of the winding 12 and between that winding and the two sectionsof the winding 11 and it isinducedin opposite directions at any instantin these two spaces. Not all of the flux in either of these spaces,however, may return through the other space. Some of the flux tends toleave the windings and returnthrough the easiest outside path as hasalready been explained. The conductive members 13 connected by theconductors 14 largely reduces the outer magnetic" field as in the caseof the transformer shown in F ig. 1. Some' of the magnetic fluxv alsotends to return inside of the inner section of the winding 11 and muchof this flux would enter the central winding leg crosswise of itslaminations where it would cause excessive losses. Conductive members 15are therefore provided near both ends of the inner section of thewinding 11, the twomembers 15 at each end being connected into a closedcircuit by conductors 14 passing around the outer edge of the core. Thisclosed circuit will obviously prevent any substantial amount of fluxfrom returning inside the inner section of the winding 11 so that nearlyall the leakage flux will be confined to a path through the two spacesnext to the winding 12.

The inventionhas been explained by describing and illustrating itsapplication to various forms of transformers and it will be apparentthat various further changes andmodifications may be made without dearting from the scope of the invention as de med in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A transformer including a core'having a win-ding leg, two spacedconcentric windings surrounding said winding leg, and a conductivemember extending along and close to an end of the outer of saidwindings, the ends of said conductive member being connected to form aclosed circuit in front of the space between said windings.

2. A transformer including a core having a winding leg, two spacedconcentric windings surrounding said winding leg, and a conductivemember extendingalong and close to an end of the outer of said windingson each side.

of said core, said conductive members being connected around the outeredge of said core to form a closed circuit in front of the space betweensaid windings.-

3. A transformer including a core having a winding leg, two spacedconcentric windings surrounding said winding leg, and a conductivemember extending along and close to each end of the outer of saidwindings on each side of said core, said conductive members beingconnected around the outer edge of said core to form a closed circuit infront of each end of the space between said windings.

4. A transformer including a core having a winding leg, two concentricwindings,

GUGLIELMO CAMILLI.

